Spinal cord stimulation (SCS) is used to treat a wide range of chronic neuropathic pain conditions by delivering electrical stimulation to select portions of the spinal cord. In the past, SCS therapy has been proposed in which a tonic therapy is delivered having continuous pulses have a select frequency, pulse width and intensity. By way of example, tonic therapies have been proposed to manage cervical and lumbar pain. The frequency, pulse width and intensity may be changed, along with electrode configuration and placement on the spinal column in connection with pain relief for individual patients.
NS systems are devices that generate electrical pulses and deliver the pulses to nervous tissue to treat a variety of disorders. For example, spinal cord stimulation has been used to treat chronic and intractable pain. Another example is deep brain, stimulation, which has been used to treat movement disorders such as Parkinson's disease and affective disorders such as depression. While a precise understanding of the interaction between the applied electrical energy and the nervous tissue is not fully appreciated, it is known that application of electrical pulses to certain regions or areas of nervous tissue can effectively mask certain types of pain transmitted from regions, increase the production of neurotransmitters, or the like. For example, applying electrical energy to the spinal cord associated with regions of the body afflicted with chronic pain can induce “paresthesia” (a subjective sensation of numbness or tingling) in the afflicted bodily regions. Thereby, paresthesia can effectively mask the transmission of non-acute pain sensations to the brain.
An NS system has been proposed in WO 2012/155187, titled “Method and Apparatus for Application of a Neural Stimulus,” to John Parker at al. According to an aspect, the '187 application provides a method of applying a neural stimulus to yield a therapeutic effect while suppressing psychophysical side effects by delivering a first stimulus to recruit a portion of the A-beta fiber population and a second stimulus, delivered within the refractory period following the first stimulus, to recruit a further portion of the A-beta fiber population. The '187 application describes stimulation at successively larger and larger pulse amplitudes to recruit successively more A-beta fibers. The '187 application describes that pulses are timed so that later pulses occur in the refractory period of excited A-beta fibers from the previous pulse in order that different subpopulations of the A-beta fibers can be selected with each pulse.
However, in at least some patients, it may not be desirable for tonic stimulation to induce paresthesia. For example, paresthesia causes discomfort and irritation in many patients. Therefore, in many instances, it is not preferable to deliver stimulation at successively larger and larger pulse amplitudes.
Moreover, while burst therapies may be used to reduce neuropathic pain without generating paresthesia, limited information is known regarding the relation between neuropathic pain and various aspects of burst therapy. Further, limited information is known regarding the relation between management of pain therapy and coupled operation of tonic and burst therapies.